Dialysis is a treatment used to support a patient with insufficient renal function. The two principal dialysis methods are hemodialysis and peritoneal dialysis.
During hemodialysis (“HD”), the patient's blood is passed through a dialyzer of a dialysis machine while also passing a dialysis solution or dialysate through the dialyzer. A semi-permeable membrane in the dialyzer separates the blood from the dialysate within the dialyzer and allows diffusion and osmosis exchanges to take place between the dialysate and the blood stream. These exchanges across the membrane result in the removal of waste products, including solutes like urea and creatinine, from the blood. These exchanges also regulate the levels of other substances, such as sodium and water, in the blood. In this way, the dialysis machine acts as an artificial kidney for cleansing the blood.
During peritoneal dialysis (“PD”), a patient's peritoneal cavity is periodically infused with dialysis solution or dialysate. The membranous lining of the patient's peritoneum acts as a natural semi-permeable membrane that allows diffusion and osmosis exchanges to take place between the solution and the blood stream. These exchanges across the patient's peritoneum, like the continuous exchange across the dialyzer in HD, result in the removal of waste products, including solutes like urea and creatinine, from the blood, and regulate the levels of other substances, such as sodium and water, in the blood.
Many PD machines, commonly referred to as “cyclers”, are designed to automatically infuse, dwell, and drain dialysate to and from the patient's peritoneal cavity in a process referred to as “continuous cycler-assisted peritoneal dialysis” (CCPD). The treatment typically lasts for several hours, often beginning with an initial drain procedure to empty the peritoneal cavity of used or spent dialysate. The sequence then proceeds through the succession of infusion, dwell, and drain phases that follow one after the other. Each phase is called a cycle.
Due to the length of the treatment, the large size of the PD machine and the large volume of dialysate required for the treatment, the treatment may be performed at home while the patient sleeps. Although nighttime CCPD treatments are sufficient for some patients, other patients require one or more additional fluid exchanges during the daytime. To permit the patient to participate in normal daily activities outside of the home, continuous ambulatory peritoneal dialysis (CAPD) is performed by connecting a bag of dialysis fluid to the patient's peritoneal catheter, and delivering about 1-3 liters of dialysate to the peritoneal cavity. After permitting the dialysate to dwell in the peritoneal cavity for a predetermined period of time, the dialysate is drained from the peritoneal cavity. The patient typically monitors and records the number of daytime exchanges and the amounts of dialysate used during the daytime exchanges.